feat: docker build, example docker-compose

[sammcj]

I thought I'd create a containerised build for your project.

If you're not interested feel free to reject or modify as you desire.

---

• Dockerfile for building the project as a container image.
• Example docker-compose.
• Designed for machines with CUDA, but could be modified for others.

[williamyang1991]

Wow. Thank you for your contribution!
We will look into and evaluate it. If it can help users to use the code more conveniently, we are happy to merge this feature.

[sammcj]

Yeah no worries at all, it's one of those things that is a bit dependant on how the user has their machine setup, but by containerising the application it allows people to run it or even just try it out without having to pollute their operating system with a bunch of libraries, packages etc...

There's lots of improvements that could be made (the resulting image is large but that's "ok" if you're building it yourself as people would be, it's specific to cuda/nvidia etc....) and there's bound to be some bugs but it's a starting place. As I said if you're not into it feel free to close the PR.

[SingleZombie]

I got some issues:

1. "Permission denied: 'models/gmflow_sintel-0c07dcb3.pth'". Seems the owner of models is root rather than app.
2. Cannot find app/entrypoint.sh when starting a image. I have to delete CMD ["/app/entrypoint.sh"] in the Dockerfile. Maybe this issue will be resolved after the PR merged.